Regional Variability of Moist Thermodynamics and Energy Associated with Transient Changes in Easterly Waves

Abstract Across the tropics, westward-propagating disturbances known as tropical easterly waves (TEWs) make large impacts at regional and global scales. Most TEW studies focus on one domain, limiting the ability to make regional comparisons. In addition, the unique regional background states of TEWs can result in sensitivities for processes related to wave amplification and decay. In this work, we examine convective characteristics and processes related to wave intensity change in four active TEW regions. Specifically, we use a TEW database that tracks low-level curvature vorticity (CV) features in MERRA-2 from 2000 to 2020. Using regional thresholds for fractional changes in CV, we first identify amplifying and decaying waves. We then compare large-scale processes through moist static energy (MSE) budget analysis and local features including vertical structures of humidity, winds, and latent heating. Horizontal MSE advection and vertical MSE advection contain key differences between amplifying and decaying waves. Positive horizontal advection is observed west of the kinematic wave center, while strong negative advection is located at and to the southeast. Vertical MSE advection is enhanced at the wave center for amplifying waves in most regions and is especially pronounced for northeast Pacific and Indian Ocean amplifying waves. Cross sections of relative humidity and winds confirm the importance of the local vertical moisture transport for amplifying waves. Finally, structures of latent heating highlight the role of local moist convection associated with wave intensification as all regions contain enhanced positive eddy kinetic energy tendencies at low levels that were likely generated below latent heating maxima for amplifying waves.